As is well known, punch presses are highly useful for producing various types of cutouts in sheet-like workpieces of metal, plastic, composite materials, and the like. In recent years, numerically controlled punch presses have enabled the production of relatively complex cutouts by repetitive punch strokes in nibbling operations, because movement of a workpiece clamping mechanism may be controlled by an X-Y coordinate guidance system.
Moreover, with the advent of large turret assemblies in turret-type punch presses and with the later advent of automatic tool changer type punch presses, a fairly large amount of tooling will be provided within the press so that the operative punch and die may be readily changed. Thus, even complex configurations have been made possible through the optimization of computer numerically controlled systems in presses providing a multiplicity of interchangeable tools.
However, the configuration of cutouts that could be obtained by a punch press still has been dictated by the specific tooling available for operation without changing the tools in the turrets or in the tool changer carriers, and it has generally been necessary to change the tooling in the operative ram position in order to effect any modification in the cutout being produced. More recently in Hirata at al, U.S. Pat. No. 4,412,469 granted Nov. 1, 1983, it has been proposed to provide additional variation in the nature of the punching operation by a rotatable set of tooling in a turret-type punch press. More particularly, at the two diametrically spaced positions in the turrets, there has been provided tooling which can be rotated by a pair of servomotors. As a result, rotation of the tooling may be coupled with the indexing of the workpiece to produce cutouts at different angular relationships.
Although this turret-type apparatus does afford the opportunity for changing the angular position of the tooling in the operative location below the ram, it is subject to the requirement that the tooling be changed in the turrets in those positions which have the drive mechanism for rotating the tooling. Moreover, the provision of drive mechanisms for each of the turrets significantly reduces the amount of tooling that is stored therein. Additionally, turret-type punch presses inherently afford less control over the movement of the punch so that increased wear may be expected, which may be compounded by the requirements for the rotational coupling to effect the desired rotational movement.
It is an object of the present invention to provide a novel and rugged punch press wherein the punch tooling is rigidly coupled to the lower portion of the ram assembly so as to move integrally therewith and to provide a mechanism which effects rotation of the lower portion of the ram and thereby be the punching.
It is also an object to provide such a press in which the die holder assembly securely receives the die in alignment with the cooperating punch and in which the die holder assembly is rotated to effect the rotation of the die simultaneously with the rotation of the punch.
Another object is to provide such a punch press which ensures precise rotation of the punch and die n unison to avoid misalignment.
A further object is to provide a novel method of punching sheet-like workpieces so as to form relatively complex and large cutouts in the sheet-like workpiece at a rapid rate with limited sets of tooling.